block/qed-check.c

   1 /*
   2  * QEMU Enhanced Disk Format Consistency Check
   3  *
   4  * Copyright IBM, Corp. 2010
   5  *
   6  * Authors:
   7  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include "qemu/osdep.h"
  15 #include "qed.h"
  16
  17 typedef struct {
  18     BDRVQEDState *s;
  19     BdrvCheckResult *result;
  20     bool fix;                           /* whether to fix invalid offsets */
  21
  22     uint64_t nclusters;
  23     uint32_t *used_clusters;            /* referenced cluster bitmap */
  24
  25     QEDRequest request;
  26 } QEDCheck;
  27
  28 static bool qed_test_bit(uint32_t *bitmap, uint64_t n) {
  29     return !!(bitmap[n / 32] & (1 << (n % 32)));
  30 }
  31
  32 static void qed_set_bit(uint32_t *bitmap, uint64_t n) {
  33     bitmap[n / 32] |= 1 << (n % 32);
  34 }
  35
  36 /**
  37  * Set bitmap bits for clusters
  38  *
  39  * @check:          Check structure
  40  * @offset:         Starting offset in bytes
  41  * @n:              Number of clusters
  42  */
  43 static bool qed_set_used_clusters(QEDCheck *check, uint64_t offset,
  44                                   unsigned int n)
  45 {
  46     uint64_t cluster = qed_bytes_to_clusters(check->s, offset);
  47     unsigned int corruptions = 0;
  48
  49     while (n-- != 0) {
  50         /* Clusters should only be referenced once */
  51         if (qed_test_bit(check->used_clusters, cluster)) {
  52             corruptions++;
  53         }
  54
  55         qed_set_bit(check->used_clusters, cluster);
  56         cluster++;
  57     }
  58
  59     check->result->corruptions += corruptions;
  60     return corruptions == 0;
  61 }
  62
  63 /**
  64  * Check an L2 table
  65  *
  66  * @ret:            Number of invalid cluster offsets
  67  */
  68 static unsigned int qed_check_l2_table(QEDCheck *check, QEDTable *table)
  69 {
  70     BDRVQEDState *s = check->s;
  71     unsigned int i, num_invalid = 0;
  72     uint64_t last_offset = 0;
  73
  74     for (i = 0; i < s->table_nelems; i++) {
  75         uint64_t offset = table->offsets[i];
  76
  77         if (qed_offset_is_unalloc_cluster(offset) ||
  78             qed_offset_is_zero_cluster(offset)) {
  79             continue;
  80         }
  81         check->result->bfi.allocated_clusters++;
  82         if (last_offset && (last_offset + s->header.cluster_size != offset)) {
  83             check->result->bfi.fragmented_clusters++;
  84         }
  85         last_offset = offset;
  86
  87         /* Detect invalid cluster offset */
  88         if (!qed_check_cluster_offset(s, offset)) {
  89             if (check->fix) {
  90                 table->offsets[i] = 0;
  91                 check->result->corruptions_fixed++;
  92             } else {
  93                 check->result->corruptions++;
  94             }
  95
  96             num_invalid++;
  97             continue;
  98         }
  99
 100         qed_set_used_clusters(check, offset, 1);
 101     }
 102
 103     return num_invalid;
 104 }
 105
 106 /**
 107  * Descend tables and check each cluster is referenced once only
 108  */
 109 static int qed_check_l1_table(QEDCheck *check, QEDTable *table)
 110 {
 111     BDRVQEDState *s = check->s;
 112     unsigned int i, num_invalid_l1 = 0;
 113     int ret, last_error = 0;
 114
 115     /* Mark L1 table clusters used */
 116     qed_set_used_clusters(check, s->header.l1_table_offset,
 117                           s->header.table_size);
 118
 119     for (i = 0; i < s->table_nelems; i++) {
 120         unsigned int num_invalid_l2;
 121         uint64_t offset = table->offsets[i];
 122
 123         if (qed_offset_is_unalloc_cluster(offset)) {
 124             continue;
 125         }
 126
 127         /* Detect invalid L2 offset */
 128         if (!qed_check_table_offset(s, offset)) {
 129             /* Clear invalid offset */
 130             if (check->fix) {
 131                 table->offsets[i] = 0;
 132                 check->result->corruptions_fixed++;
 133             } else {
 134                 check->result->corruptions++;
 135             }
 136
 137             num_invalid_l1++;
 138             continue;
 139         }
 140
 141         if (!qed_set_used_clusters(check, offset, s->header.table_size)) {
 142             continue; /* skip an invalid table */
 143         }
 144
 145         ret = qed_read_l2_table_sync(s, &check->request, offset);
 146         if (ret) {
 147             check->result->check_errors++;
 148             last_error = ret;
 149             continue;
 150         }
 151
 152         num_invalid_l2 = qed_check_l2_table(check,
 153                                             check->request.l2_table->table);
 154
 155         /* Write out fixed L2 table */
 156         if (num_invalid_l2 > 0 && check->fix) {
 157             ret = qed_write_l2_table_sync(s, &check->request, 0,
 158                                           s->table_nelems, false);
 159             if (ret) {
 160                 check->result->check_errors++;
 161                 last_error = ret;
 162                 continue;
 163             }
 164         }
 165     }
 166
 167     /* Drop reference to final table */
 168     qed_unref_l2_cache_entry(check->request.l2_table);
 169     check->request.l2_table = NULL;
 170
 171     /* Write out fixed L1 table */
 172     if (num_invalid_l1 > 0 && check->fix) {
 173         ret = qed_write_l1_table_sync(s, 0, s->table_nelems);
 174         if (ret) {
 175             check->result->check_errors++;
 176             last_error = ret;
 177         }
 178     }
 179
 180     return last_error;
 181 }
 182
 183 /**
 184  * Check for unreferenced (leaked) clusters
 185  */
 186 static void qed_check_for_leaks(QEDCheck *check)
 187 {
 188     BDRVQEDState *s = check->s;
 189     uint64_t i;
 190
 191     for (i = s->header.header_size; i < check->nclusters; i++) {
 192         if (!qed_test_bit(check->used_clusters, i)) {
 193             check->result->leaks++;
 194         }
 195     }
 196 }
 197
 198 /**
 199  * Mark an image clean once it passes check or has been repaired
 200  */
 201 static void qed_check_mark_clean(BDRVQEDState *s, BdrvCheckResult *result)
 202 {
 203     /* Skip if there were unfixable corruptions or I/O errors */
 204     if (result->corruptions > 0 || result->check_errors > 0) {
 205         return;
 206     }
 207
 208     /* Skip if image is already marked clean */
 209     if (!(s->header.features & QED_F_NEED_CHECK)) {
 210         return;
 211     }
 212
 213     /* Ensure fixes reach storage before clearing check bit */
 214     bdrv_flush(s->bs);
 215
 216     s->header.features &= ~QED_F_NEED_CHECK;
 217     qed_write_header_sync(s);
 218 }
 219
 220 /* Called with table_lock held.  */
 221 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix)
 222 {
 223     QEDCheck check = {
 224         .s = s,
 225         .result = result,
 226         .nclusters = qed_bytes_to_clusters(s, s->file_size),
 227         .request = { .l2_table = NULL },
 228         .fix = fix,
 229     };
 230     int ret;
 231
 232     check.used_clusters = g_try_new0(uint32_t, (check.nclusters + 31) / 32);
 233     if (check.nclusters && check.used_clusters == NULL) {
 234         return -ENOMEM;
 235     }
 236
 237     check.result->bfi.total_clusters =
 238         DIV_ROUND_UP(s->header.image_size, s->header.cluster_size);
 239     ret = qed_check_l1_table(&check, s->l1_table);
 240     if (ret == 0) {
 241         /* Only check for leaks if entire image was scanned successfully */
 242         qed_check_for_leaks(&check);
 243
 244         if (fix) {
 245             qed_check_mark_clean(s, result);
 246         }
 247     }
 248
 249     g_free(check.used_clusters);
 250     return ret;
 251 }